Concept: Aggression

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Many high-profile societal problems involve an individual or group repeatedly attacking another - from child-parent disputes, sexual violence against women, civil unrest, violent conflicts and acts of terror, to current cyber-attacks on national infrastructure and ultrafast cyber-trades attacking stockholders. There is an urgent need to quantify the likely severity and timing of such future acts, shed light on likely perpetrators, and identify intervention strategies. Here we present a combined analysis of multiple datasets across all these domains which account for >100,000 events, and show that a simple mathematical law can benchmark them all. We derive this benchmark and interpret it, using a minimal mechanistic model grounded by state-of-the-art fieldwork. Our findings provide quantitative predictions concerning future attacks; a tool to help detect common perpetrators and abnormal behaviors; insight into the trajectory of a ‘lone wolf’; identification of a critical threshold for spreading a message or idea among perpetrators; an intervention strategy to erode the most lethal clusters; and more broadly, a quantitative starting point for cross-disciplinary theorizing about human aggression at the individual and group level, in both real and online worlds.

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Antisocial and criminal behaviors are multifactorial traits whose interpretation relies on multiple disciplines. Since these interpretations may have social, moral and legal implications, a constant review of the evidence is necessary before any scientific claim is considered as truth. A recent study proposed that men with wider faces relative to facial height (fWHR) are more likely to develop unethical behaviour mediated by a psychological sense of power. This research was based on reports suggesting that sexual dimorphism and selection would be responsible for a correlation between fWHR and aggression. Here we show that 4,960 individuals from 94 modern human populations belonging to a vast array of genetic and cultural contexts do not display significant amounts of fWHR sexual dimorphism. Further analyses using populations with associated ethnographical records as well as samples of male prisoners of the Mexico City Federal Penitentiary condemned by crimes of variable level of inter-personal aggression (homicide, robbery, and minor faults) did not show significant evidence, suggesting that populations/individuals with higher levels of bellicosity, aggressive behaviour, or power-mediated behaviour display greater fWHR. Finally, a regression analysis of fWHR on individual’s fitness showed no significant correlation between this facial trait and reproductive success. Overall, our results suggest that facial attributes are poor predictors of aggressive behaviour, or at least, that sexual selection was weak enough to leave a signal on patterns of between- and within-sex and population facial variation.

Previous research has pointed towards a link between emotion dysregulation and aggressive behavior in children. Emotion regulation difficulties are not specific for children with persistent aggression problems, i.e. oppositional defiant disorder or conduct disorder (ODD/CD), children with other psychiatric conditions, such as autism spectrum disorders or attention-deficit/hyperactivity disorder, have emotion regulation difficulties too. On a behavioral level some overlap exists between these disorders and comorbidity is high. The aim of this study was therefore twofold: 1) to examine emotion regulation difficulties in 65 boys with ODD/CD in comparison to a non-clinical control group (NC) of 38 boys (8-12 years) using a performance measure (Ultimatum Game), parent report and self-report, and 2) to establish to what extent emotion regulation in the ODD/CD group was correlated with severity of autism and/or attention deficit traits. Results on the Ultimatum Game showed that the ODD/CD group rejected more ambiguous offers than the NC group, which is seen as an indication of poor emotion regulation. Parents also reported that the ODD/CD group experienced more emotion regulation problems in daily life than the NC group. In contrast to these cognitive and behavioral measures, self-reports did not reveal any difference, indicating that boys with ODD/CD do not perceive themselves as having impairments in regulating their emotions. Emotional decision making within the ODD/CD group was not related to variation in autism or attention deficit traits. These results support the idea that emotion dysregulation is an important problem within ODD/CD, yet boys with ODD/CD have reduced awareness of this.

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Actors of public interest today have to fear the adverse impact that stems from social media platforms. Any controversial behavior may promptly trigger temporal, but potentially devastating storms of emotional and aggressive outrage, so called online firestorms. Popular targets of online firestorms are companies, politicians, celebrities, media, academics and many more. This article introduces social norm theory to understand online aggression in a social-political online setting, challenging the popular assumption that online anonymity is one of the principle factors that promotes aggression. We underpin this social norm view by analyzing a major social media platform concerned with public affairs over a period of three years entailing 532,197 comments on 1,612 online petitions. Results show that in the context of online firestorms, non-anonymous individuals are more aggressive compared to anonymous individuals. This effect is reinforced if selective incentives are present and if aggressors are intrinsically motivated.

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Despite its essential role in human coexistence, the developmental origins and progression of sympathy in infancy are not yet fully understood. We show that preverbal 10-month-olds manifest sympathetic responses, evinced in their preference for attacked others according to their evaluations of the respective roles of victim, aggressor, and neutral party. In Experiment 1, infants viewing an aggressive social interaction between a victim and an aggressor exhibited preference for the victim. In Experiment 2, when comparing the victim and the aggressor to a neutral object, infants preferred the victim and avoided the aggressor. These findings indicate that 10-month-olds not only evaluate the roles of victims and aggressors in interactions but also show rudimentary sympathy toward others in distress based on that evaluation. This simple preference may function as a foundation for full-fledged sympathetic behavior later on.

Overconsumption of sugar-sweetened beverages (SSBs) is known to be a key contributor to the obesity epidemic; however, its effects on behavioral changes are yet to be fully studied. In the present study, we examined the long-term effects of SSB on social aggression in mice. Three-week-old weaned mice started to drink either a 30 w/v% sucrose solution (S30), plain water (CT), or an aspartame solution with sweetness equivalent to the sucrose solution (A30) and continued to drink until they were 11-week-old adults. Aggressive behaviors were assessed by the resident-intruder test. We found that SSB significantly promoted social aggression, accompanied by heightened serum corticosterone and reduced body weight. To understand the underlying mechanism, we performed transcriptome analyses of brain. The profiles of mice on S30 were dramatically different from those on CT or A30. Transcriptional networks related to immunological function were significantly dysregulated by SSB. FACS analysis of mice on S30 revealed increased numbers of inflammatory cells in peripheral blood. Interestingly, the artificial sweetener failed to mimic the effects of sugar on social aggression and inflammatory responses. These results demonstrate that SSB promotes aggressive behaviors and provide evidence that sugar reduction strategies may be useful in efforts to prevent social aggression.

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Intimate partner violence affects millions of people globally. One possible contributing factor is poor self-control. Self-control requires energy, part of which is provided by glucose. For 21 days, glucose levels were measured in 107 married couples. To measure aggressive impulses, each evening participants stuck between 0 and 51 pins into a voodoo doll that represented their spouse, depending how angry they were with their spouse. To measure aggression, participants competed against their spouse on a 25-trial task in which the winner blasted the loser with loud noise through headphones. As expected, the lower the level of glucose in the blood, the greater number of pins participants stuck into the voodoo doll, and the higher intensity and longer duration of noise participants set for their spouse.

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Repeated experience of winning in a social conflict setting elevates levels of aggression and may lead to violent behavioral patterns. Here, we use a paradigm of repeated aggression and fighting deprivation to examine changes in behavior, neurogenesis, and neuronal activity in mice with positive fighting experience. We show that for males, repeated positive fighting experience induces persistent demonstration of aggression and stereotypic behaviors in daily agonistic interactions, enhances aggressive motivation, and elevates levels of anxiety. When winning males are deprived of opportunities to engage in further fights, they demonstrate increased levels of aggressiveness. Positive fighting experience results in increased levels of progenitor cell proliferation and production of young neurons in the hippocampus. This increase is not diminished after a fighting deprivation period. Furthermore, repeated winning experience decreases the number of activated (c-fos-positive) cells in the basolateral amygdala and increases the number of activated cells in the hippocampus; a subsequent no-fight period restores the number of c-fos-positive cells. Our results indicate that extended positive fighting experience in a social conflict heightens aggression, increases proliferation of neuronal progenitors and production of young neurons in the hippocampus, and decreases neuronal activity in the amygdala; these changes can be modified by depriving the winners of the opportunity for further fights.

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OBJECTIVE:Few studies have comprehensively examined weight-based victimization (WBV) in youth, despite its serious consequences for their psychosocial and physical health. Given that obese and treatment-seeking youth may be highly vulnerable to WBV and its negative consequences, the current study provides a comprehensive assessment of WBV in a weight loss treatment-seeking sample.METHODS:Adolescents (aged 14-18 years; N = 361) enrolled in 2 national weight loss camps were surveyed. An in-depth assessment of WBV was conducted by using an online survey, in which participants indicated the duration, typical locations, frequent perpetrators, and forms of WBV they had experienced.RESULTS:Findings indicate that 64% of the study participants reported WBV at school, and the risk of WBV increased with body weight. Most participants reported WBV enduring for 1 year (78%), and 36% were teased/bullied for 5 years. Peers (92%) and friends (70%) were the most commonly reported perpetrators, followed by adult perpetrators, including physical education teachers/sport coaches (42%), parents (37%), and teachers (27%). WBV was most frequently reported in the form of verbal teasing (75%-88%), relational victimization (74%-82%), cyberbullying (59%-61%), and physical aggression (33%-61%). WBV was commonly experienced in multiple locations at school.CONCLUSIONS:WBV is a prevalent experience for weight loss treatment-seeking youth, even when they are no longer overweight. Given the frequent reports of WBV from adult perpetrators in addition to peers, treatment providers and school personnel can play an important role in identifying and supporting youth who may be at risk for pervasive teasing and bullying.

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Based on neuroanatomical indices such as brain size and encephalization quotient, orcas are among the most intelligent animals on Earth. They display a range of complex behaviors indicative of social intelligence, but these are difficult to study in the open ocean where protective laws may apply, or in captivity, where access is constrained for commercial and safety reasons. From 1979 to 1980, however, we were able to interact with juvenile orcas in an unstructured way at San Diego’s SeaWorld facility. We observed in the animals what appeared to be pranks, tests of trust, limited use of tactical deception, emotional self-control, and empathetic behaviors. Our observations were consistent with those of a former Seaworld trainer, and provide important insights into orca cognition, communication, and social intelligence. However, after being trained as performers within Seaworld’s commercial entertainment program, a number of orcas began to exhibit aggressive behaviors. The orcas who previously established apparent friendships with humans were most affected, although significant aggression also occurred in some of their descendants, and among the orcas they lived with. Such oceanaria confinement and commercial use can no longer be considered ethically defensible, given the current understanding of orcas' advanced cognitive, social, and communicative capacities, and of their behavioral needs.